A wide variety of methods and standards are known in the art for encoding information in a form that can be read by a computer using an image sensor or other type of optical sensor. The best-known standards of this sort are barcodes, including the traditional one-dimensional arrays of stripes and two-dimensional barcodes, such as QR codes.
Other types of image-based computer-readable encoding schemes and symbols have been proposed in the patent literature. Some of these schemes use color information, rather than the monochrome symbols provided by conventional barcodes. Representative examples are described in U.S. Pat. Nos. 7,936,901, 5,869,828 and 7,020,327.